(1) Field of the Invention
This invention relates to aromatic polyamides containing ether linkages and a process for producing the same. More particularly, the invention relates to ether linkage-containing aromatic polyamides having a melt flowability, namely a melt moldability and molded articles of the same, and process for producing the polyamides by polycondensation polymerization.
(2) Description of the Prior Art
It is well known that wholly aromatic polyamides have a higher melting point and a higher heat resistance than aliphatic polyamides. However, wholly aromatic polyamides are insoluble in organic solvents without the aid of a solution promoter such as LiCl or CaCl.sub.2, and such polyamides have no softening point and hence, are infusible. Accordingly, their application range as molding materials is considerably limited.
U.S. Pat. Nos. 3,503,931 and 3,505,288 disclose aromatic polyamides containing ether linkages, which are soluble in polar organic solvents even in the absence of a solution promotor and have a high melting points, and also disclose a polymerization process for preparing such aromatic polyamides.
The polymerization process disclosed in these U.S. Patents comprises the step of reacting an aromatic diamine containing ether linkages with an aromatic dicarboxylic acid dihalide in a polar organic solvent at such a low temperature as not exceeding 5.degree. C. and the step of eliminating the hydrogen halide formed at the reaction of the first step. In short, in the process of these U.S. Patents, aromatic polyamides containing ether linkages are prepared by a low temperature solution polymerization process.
In this known polymerization process, a high-molecular-weight aromatic polyamide containing ether linkages cannot be obtained unless the temperature is maintained at a low level not exceeding 5.degree. C. at the initial stage of reaction between an aromatic diamine containing ether linkages as a first starting substance and an aromatic carboxylic acid halide as a second starting substance. Accordingly, provision of a device controlling the temperature of the reaction vessel at this level is indispensable in this known polymerization process.
Further, in this known polymerization process, an acid collector (acid acceptor) must be used for collecting the hydrogen halide formed by the reaction between the first and second starting substances, and even is such collector is used, the hydrogen halide or its salt is left in the final product, namely the intended polyamide containing ether linkages. Accordingly, an additional step is necessary for eliminating such hydrogen halide and its salt.